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Facial features of individuals with C-terminal truncating variants in MN1, illustrating how features evolve from before to after age five years. Frontal bossing may be more prominent at infancy, with a tall forehead at later stages. Skull shape anomalies (dolichocephaly, turricephaly, and/or bitemporal narrowing, plagiocephaly, and macrocephaly) may be observed with or without underlying craniosynostosis. Other characteristic features include midface hypoplasia, downslanting palpebral fissures, hypertelorism, exophthalmia, short upturned nose, and small low-set ears (with the upper portion of the pinna frequently dysplastic). Oral-maxillofacial features include a high, arched palate, occasionally with striking narrow and triangular-shaped maxillary arch. Submucous cleft palate associated with a bifid uvula was observed in one individual [Mak et al 2020].

Reproduced with permission from Mak et al [2020]